Conventionally, it has been a common practice to insert a catheter into a organ of a living body such as a blood vessel to deliver the catheter's distal portion to a lesion (for example, a stenosed part), and perform diagnosis or treatment on the lesion.
Specifically, as a method of percutaneously inserting a catheter into a blood vessel, there has been known the sheath method based on the use of a sheath introducer. In the sheath method, a sheath tube of the sheath introducer is preliminarily inserted into a blood vessel, and, with the sheath tube kept in place, a catheter is inserted into the blood vessel through the lumen of the sheath tube (see, for example, Japanese Patent Laid-open No. Hei 03-168159, hereinafter referred to also as Patent Document 1). Such a method ensures that even in the case of, for example, inserting a large-diameter catheter (e.g., a balloon catheter) into a blood vessel, damage to the blood vessel can be minimized.
Ordinarily, a sheath introducer has a sheath hub connected to the proximal end of the sheath tube, and a catheter insertion port through which the catheter can be inserted, opens to the proximal end face of the sheath hub. In the condition where the sheath tube is set in place in a blood vessel, therefore, the catheter insertion port is oriented to face in a direction opposite to the direction of insertion of the sheath tube into the blood vessel. In other words, the direction of insertion of the sheath tube into the blood vessel and the direction of insertion of the catheter into the sheath introducer coincide with each other.